Currently, resonance devices using a MEMS (Micro Electro Mechanical Systems) technique are used as timing devices, for example. Such a resonance device is generally mounted on a printed circuit board that is incorporated into an electronic device such as a smartphone. The resonance device includes a lower substrate, an upper substrate that forms a cavity between the lower substrate and the upper substrate, and a resonator that is disposed within the cavity between the lower substrate and the upper substrate.
For example, Patent Document 1 (identified below) discloses an out-of-plane bending resonator having a plurality of vibration arms. In the resonator, each vibration arm is connected at a fixed end thereof to a front end of a base portion, and the base portion is connected at a rear end thereof, which is opposite to the front end thereof, to a support portion. For example, the support portion is connected to a base that is interposed between the lower substrate and the upper substrate. In the example of FIG. 1 of Patent Document 1, since electric fields to be applied to the vibration arms are set in directions opposite to each other, vibrations in opposite phases are achieved between an inner vibration arm and outer two vibration arms.
Patent Document 1: Japanese Patent No. 5071058.
However, in the existing resonance device disclosed in Patent Document 1, for example, an unwanted vibration mode (spurious mode) occurs at frequencies around a main vibration mode at a desired frequency. Accordingly, the characteristics of main vibration are degraded.